The presence in the diploidal cell line of a both chromosomes of a given pair from only one parent
Possible consequences:
- imprinting of sigle genes or chromosome region
- homozygosity for mutant allele

Genomic imprinting

Differential expression of a gene depending on whether it was inherited from the mather or the father  epigenetic control of gene expression

Does not follow simple Mendelian pattern
The recurrence risk depends on:
Degree of relationship with the proband
Severity of the proband’s disease
Number of affected individuals in the family
Sex of the proband (more commonly affected)

Segregation analysis

statistical comparison (binomial therom) of frequency and distribution of affected and unaffected individuals in families to determine the most likely mode of inheritance

Association analysis

statistical comparison to determine if a particular form of DNA polymorphism occurs more frequently in subjects with a phenotype of interest

Linkage analysis

analyze the distribution of loci within families to determine if a particular region of genome contains a gene related to the phenotype of interest

Linkage mapping

crossover frequency indicated the distance of separation on a chromosome
greater distance more frequency of crossing over, less likely to be linked
LOD score

recipricol (exchange of material between nonhomologous chromosomes)
Robertsonian (long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost)
13, 14, 15, 21, and 22

Dynamic mutation

unstable heritable element where the probability of mutation is a function of the number of copies of the mutation